Dr. Tracy’s research interests focus on the measurement and analysis of juvenile delinquencycareers, legal and policyissues in juvenile justice, prediction models of criminal careers, and drug prohibition policy. He is a recognized expert in the application of longitudinal research designs to the study of delinquent and criminal careers. His study of a large Philadelphia birth cohort of 27,160 people is the largest study of delinquency and crime ever conducted and is now in its 32nd year. Through his research he has developed particular expertise in studying the origins of criminal careers and the factors associated with becoming a chronic recidivist. Dr. Tracy has published seven books and numerous articles in criminology journals.